The Diocese of Niagara is one of thirty regional divisions in the Anglican Church of Canada. The see city of the diocese is Hamilton, with the bishop's cathedra located at Christ's Church Cathedral on James Street North. Located within the ecclesiastical province of Ontario, it borders the Dioceses of Huron and Toronto. The area enclosed by the Diocese of Niagara includes much of the Golden Horseshoe, and moves north to include Erin and Orangeville as far as Shelburne. Moving sharply south, the boundary includes Mount Forest and widens, south-westerly to include Elora and Guelph. Skirting Brantford and the Territory of the Six Nations Confederacy, the line then travels, again, south-westerly to Jarvis and Lake Erie to include the entire Niagara Peninsula. Major urban centres within its borders are St. Catharines, Niagara Falls, Hamilton, Guelph, Oakville, Milton, Burlington, and Orangeville.

The Anglican Church of Canada is the province of the Anglican Communion in Canada. The official French-language name is l'Église anglicane du Canada. In 2022, the Anglican Church counted 294,931 members on parish rolls in 1,978 congregations, organized into 1,498 parishes. The 2021 Canadian census counted 1,134,315 self-identified Anglicans, making the Anglican Church the third-largest Canadian church after the Catholic Church and the United Church of Canada.